The problem can be corrected by upgrading the affected package to version 1.0.4-3ubuntu1.1 (for Ubuntu 4.10), or 1.0.16-13ubuntu0.1 (for Ubuntu 5.04). For most desktop applications, a standard system upgrade is sufficient to effect the necessary changes. However, if you are using server and long running applications that use libgnutls (cupsys, exim4, Gaim), you must restart them manually. If you can afford to reboot your machine, this is the easiest way to ensure that all services using this library are restarted correctly.

Details follow:

A Denial of Service vulnerability was discovered in the GNU TLS library, which provides common cryptographic algorithms and is used by many applications in Ubuntu. Due to a missing sanity check of the padding length field, specially crafted ciphertext blocks caused an out of bounds memory access which could crash the application. It was not possible to exploit this to execute any attacker specified code.